Physiological measurement communications adapter

ABSTRACT

A sensor interface is configured to receive a sensor signal. A transmitter modulates a first baseband signal responsive to the sensor signal so as to generate a transmit signal. A receiver demodulates a receive signal corresponding to the transmit signal so as to generate a second baseband signal corresponding to the first baseband signal. Further, a monitor interface is configured to communicate a waveform responsive to the second baseband signal to a sensor port of a monitor. The waveform is adapted to the monitor so that measurements derived by the monitor from the waveform are generally equivalent to measurements derivable from the sensor signal. The communications adapter may further comprise a signal processor having an input in communications with the sensor interface, where the signal processor is operable to derive a parameter responsive to the sensor signal and where the first baseband signal is responsive to the parameter. The parameter may correspond to at least one of a measured oxygen saturation and a pulse rate.

REFERENCE TO RELATED APPLICATION

The present application claims priority benefit under 35 U.S.C. § 120to, and is a continuation of, U.S. patent application Ser. No.10/377,933, filed Feb. 28, 2003, entitled “Physiological MeasurementCommunications Adapter,” now U.S. Pat. No. 6,850,788, which claimspriority benefit under 35 U.S.C. § 119(e) from U.S. ProvisionalApplication Ser. No. 60/367,428, filed Mar. 25, 2002, entitled“Physiological Measurement Communications Adapter.” The presentapplication also incorporates the foregoing disclosures herein byreference.

BACKGROUND OF THE INVENTION

Patient vital sign monitoring may include measurements of blood oxygen,blood pressure, respiratory gas, and EKG among other parameters. Each ofthese physiological parameters typically require a sensor in contactwith a patient and a cable connecting the sensor to a monitoring device.For example, FIGS. 1-2 illustrate a conventional pulse oximetry system100 used for the measurement of blood oxygen. As shown in FIG. 1, apulse oximetry system has a sensor 110, a patient cable 140 and amonitor 160. The sensor 110 is typically attached to a finger 10 asshown. The sensor 110 has a plug 118 that inserts into a patient cablesocket 142. The monitor 160 has a socket 162 that accepts a patientcable plug 144. The patient cable 140 transmits an LED drive signal 252(FIG. 2) from the monitor 160 to the sensor 110 and a resulting detectorsignal 254 (FIG. 2) from the sensor 110 to the monitor 160. The monitor160 processes the detector signal 254 (FIG. 2) to provide, typically, anumerical readout of the patient's oxygen saturation, a numericalreadout of pulse rate, and an audible indicator or “beep” that occurs inresponse to each arterial pulse.

As shown in FIG. 2, the sensor 110 has both red and infrared LEDemitters 212 and a photodiode detector 214. The monitor 160 has a sensorinterface 271, a signal processor 273, a controller 275, output drivers276, a display and audible indicator 278, and a keypad 279. The monitor160 determines oxygen saturation by computing the differentialabsorption by arterial blood of the two wavelengths emitted by thesensor emitters 212, as is well-known in the art. The sensor interface271 provides LED drive current 252 which alternately activates the redand IR LED emitters 212. The photodiode detector 214 generates a signal254 corresponding to the red and infrared light energy attenuated fromtransmission through the patient finger 10 (FIG. 1). The sensorinterface 271 also has input circuitry for amplification, filtering anddigitization of the detector signal 254. The signal processor 273calculates a ratio of detected red and infrared intensities, and anarterial oxygen saturation value is empirically determined based on thatratio. The controller 275 provides hardware and software interfaces formanaging the display and audible indicator 278 and keypad 279. Thedisplay and audible indicator 278 shows the computed oxygen status, asdescribed above, and provides the pulse beep as well as alarmsindicating oxygen desaturation events. The keypad 279 provides a userinterface for setting alarm thresholds, alarm enablement, and displayoptions, to name a few.

SUMMARY OF THE INVENTION

Conventional physiological measurement systems are limited by thepatient cable connection between sensor and monitor. A patient must belocated in the immediate vicinity of the monitor. Also, patientrelocation requires either disconnection of monitoring equipment and acorresponding loss of measurements or an awkward simultaneous movementof patient equipment and cables. Various devices have been proposed orimplemented to provide wireless communication links between sensors andmonitors, freeing patients from the patient cable tether. These devices,however, are incapable of working with the large installed base ofexisting monitors and sensors, requiring caregivers and medicalinstitutions to suffer expensive wireless upgrades. It is desirable,therefore, to provide a communications adapter that is plug-compatibleboth with existing sensors and monitors and that implements a wirelesslink replacement for the patient cable.

An aspect of a physiological measurement communications adaptercomprises a sensor interface configured to receive a sensor signal. Atransmitter modulates a first baseband signal responsive to the sensorsignal so as to generate a transmit signal. A receiver demodulates areceive signal corresponding to the transmit signal so as to generate asecond baseband signal corresponding to the first baseband signal.Further, a monitor interface is configured to communicate a waveformresponsive to the second baseband signal to a sensor port of a monitor.The waveform is adapted to the monitor so that measurements derived bythe monitor from the waveform are generally equivalent to measurementsderivable from the sensor signal. The communications adapter may furthercomprise a signal processor having an input in communications with thesensor interface, where the signal processor is operable to derive aparameter responsive to the sensor signal and where the first basebandsignal is responsive to the parameter. The parameter may correspond toat least one of a measured oxygen saturation and a pulse rate.

One embodiment may further comprise a waveform generator thatsynthesizes the waveform from a predetermined shape. The waveformgenerator synthesizes the waveform at a frequency adjusted to begenerally equivalent to the pulse rate. The waveform may have a firstamplitude and a second amplitude, and the waveform generator may beconfigured to adjusted the amplitudes so that measurements derived bythe monitor are generally equivalent to a measured oxygen saturation.

In another embodiment, the sensor interface is operable on the sensorsignal to provide a plethysmograph signal output, where the firstbaseband signal is responsive to the plethysmograph signal. Thisembodiment may further comprise a waveform modulator that modifies adecoded signal responsive to the second baseband signal to provide thewaveform. The waveform modulator may comprise a demodulator thatseparates a first signal and a second signal from the decoded signal, anamplifier that adjusts amplitudes of the first and second signals togenerate a first adjusted signal and a second adjusted signal, and amodulator that combines the first and second adjusted signals into thewaveform. The amplitudes of the first and second signals may beresponsive to predetermined calibration data for the sensor and themonitor.

An aspect of a physiological measurement communications adapter methodcomprises the steps of inputting a sensor signal at a patient location,communicating patient data derived from the sensor signal between thepatient location and a monitor location, constructing a waveform at themonitor location responsive to the sensor signal, and providing thewaveform to a monitor via a sensor port. The waveform is constructed sothat the monitor calculates a parameter generally equivalent to ameasurement derivable from the sensor signal.

In one embodiment, the communicating step may comprise the substeps ofderiving a conditioned signal from the sensor signal, calculating aparameter signal from the conditioned signal, and transmitting theparameter signal from the patient location to the monitor location. Theconstructing step may comprise the substep of synthesizing the waveformfrom the parameter signal. In an alternative embodiment, thecommunicating step may comprise the substeps of deriving a conditionedsignal from said sensor signal and transmitting the conditioned signalfrom the patient location to the monitor location. The constructing stepmay comprise the substeps of demodulating the conditioned signal andre-modulating the conditioned signal to generate the waveform. Theproviding step may comprise the substeps of inputting a monitor signalfrom an LED drive output of the sensor port, modulating the waveform inresponse to the monitor signal, and outputting the waveform on adetector input of the sensor port.

Another aspect of a physiological measurement communications adaptercomprises a sensor interface means for inputting a sensor signal andoutputting a conditioned signal, a transmitter means for sending dataresponsive to the sensor signal, and a receiver means for receiving thedata. The communications adapter further comprises a waveform processormeans for constructing a waveform from the data so that measurementsderived by a monitor from the waveform are generally equivalent tomeasurements derivable from the sensor signal, and a monitor interfacemeans for communicating the waveform to a sensor port of the monitor.The communications adapter may further comprise a signal processor meansfor deriving a parameter signal from the conditioned signal, where thedata comprises the parameter signal. The waveform processor means maycomprise a means for synthesizing the waveform from the parametersignal. The data may comprise the conditioned signal, and the waveformprocessor means may comprise a means for modulating the conditionedsignal in response to the monitor.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration of a prior art pulse oximetry system;

FIG. 2 is a functional block diagram of a prior art pulse oximetrysystem;

FIG. 3 is an illustration of a physiological measurement communicationsadapter;

FIGS. 4A-B are illustrations of communications adapter sensor modules;

FIGS. 5A-C are illustrations of communications adapter monitor modules;

FIG. 6 is a functional block diagram of a communications adapter sensormodule;

FIG. 7 is a functional block diagram of a communications adapter monitormodule;

FIG. 8 is a functional block diagram of a sensor module configured totransmit measured pulse oximeter parameters;

FIG. 9 is a functional block diagram of a monitor module configured toreceived measured pulse oximeter parameters;

FIG. 10 is a functional block diagram of a sensor module configured totransmit a plethysmograph;

FIG. 11 is a functional block diagram of a monitor module configured toreceive a plethysmograph;

FIG. 12 is a functional block diagram of a waveform modulator;

FIG. 13 is a functional block diagram of a sensor module configured formultiple sensors; and

FIG. 14 is a functional block diagram of a monitor module configured formultiple sensors.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Overview

FIG. 3 illustrates one embodiment of a communications adapter. FIGS. 4-5illustrate physical configurations for a communications adapter. Inparticular, FIGS. 4A-B illustrate sensor module configurations and FIGS.5A-C illustrate monitor module configurations. FIGS. 6-14 illustratecommunications adapter functions. In particular, FIGS. 6-7 illustrategeneral functions for a sensor module and a monitor module,respectively. FIGS. 8-9 functionally illustrate a communications adapterwhere derived pulse oximetry parameters, such as saturation and pulserate are transmitted between a sensor module and a monitor module. Also,FIGS. 10-12 functionally illustrate a communications adapter where aplethysmograph is transmitted between a sensor module and a monitormodule. FIGS. 13-14 functionally illustrate a multiple-parametercommunications adapter.

FIG. 3 illustrates a communications adapter 300 having a sensor module400 and a monitor module 500. The communications adapter 300communicates patient data derived from a sensor 310 between the sensormodule 400, which is located proximate a patient 20 and the monitormodule 500, which is located proximate a monitor 360. A wireless link340 is provided between the sensor module 400 and the monitor module500, replacing the conventional patient cable, such as a pulse oximetrypatient cable 140 (FIG. 1). Advantageously, the sensor module 400 isplug-compatible with a conventional sensor 310. In particular, thesensor connector 318 connects to the sensor module 400 in a similarmanner as to a patient cable. Further, the sensor module 400 outputs adrive signal to the sensor 310 and inputs a sensor signal from thesensor 310 in an equivalent manner as a conventional monitor 360. Thesensor module 400 may be battery powered or externally powered. Externalpower may be for recharging internal batteries or for powering thesensor module during operation or both.

As shown in FIG. 3, the monitor module 500 is advantageouslyplug-compatible with a conventional monitor 360. In particular, themonitor's sensor port 362 connects to the monitor module 500 in asimilar manner as to a patient cable, such as a pulse oximetry patientcable 140 (FIG. 1). Further, the monitor module 500 inputs a drivesignal from the monitor 360 and outputs a corresponding sensor signal tothe monitor 360 in an equivalent manner as a conventional sensor 310. Assuch, the combination sensor module 400 and monitor module 500 provide aplug-compatible wireless replacement for a patient cable, adapting anexisting wired physiological measurement system into a wirelessphysiological measurement system. The monitor module 500 may be batterypowered, powered from the monitor, such as by tapping current from amonitor's LED drive, or externally powered from an independent AC or DCpower source.

Although a communications adapter 300 is described herein with respectto a pulse oximetry sensor and monitor, one of ordinary skill in the artwill recognize that a communications adapter may provide aplug-compatible wireless replace for a patient cable that connects anyphysiological sensor and corresponding monitor. For example, acommunications adapter 300 may be applied to a biopotential sensor, anon-invasive blood pressure (NIBP) sensor, a respiratory rate sensor, aglucose sensor and the corresponding monitors, to name a few.

Sensor Module Physical Configurations

FIGS. 4A-B illustrate physical embodiments of a sensor module 400. FIG.4A illustrates a wrist-mounted module 410 having a wrist strap 411, acase 412 and an auxiliary cable 420. The case 412 contains the sensormodule electronics, which are functionally described with respect toFIG. 6, below. The case 412 is mounted to the wrist strap 411, whichattaches the wrist-mounted module 410 to a patient 20. The auxiliarycable 420 mates to a sensor connector 318 and a module connector 414,providing a wired link between a conventional sensor 310 and thewrist-mounted module 410. Alternatively, the auxiliary cable 420 isdirectly wired to the sensor module 400. The wrist-mounted module 410may have a display 415 that shows sensor measurements, module status andother visual indicators, such as monitor status. The wrist-mountedmodule 410 may also have keys (not shown) or other input mechanisms tocontrol its operational mode and characteristics. In an alternativeembodiment, the sensor 310 may have a tail (not shown) that connectsdirectly to the wrist-mounted module 410, eliminating the auxiliarycable 420.

FIG. 4B illustrates a clip-on module 460 having a clip 461, a case 462and an auxiliary cable 470. The clip 461 attaches the clip-on module 460to patient clothing or objects near a patient 20, such as a bed frame.The auxiliary cable 470 mates to the sensor connector 318 and functionsas for the auxiliary cable 420 (FIG. 4A) of the wrist-mounted module 410(FIG. 4A), described above. The clip-on module 460 may have a display463 and keys 464 as for the wrist-mounted module 410 (FIG. 4A). Eitherthe wrist-mounted module 410 or the clip-on module 460 may have otherinput or output ports (not shown) that download software, configure themodule, or provide a wired connection to other measurement instrumentsor computing devices, to name a few examples.

Monitor Module Physical Configurations

FIGS. 5A-C illustrate physical embodiments of a monitor module 500. FIG.5A illustrates a direct-connect module 510 having a case 512 and anintegrated monitor connector 514. The case 512 contains the monitormodule electronics, which are functionally described with respect toFIG. 7, below. The monitor connector 514 mimics that of the monitor endof a patient cable, such as a pulse oximetry patient cable 140 (FIG. 1),and electrically and mechanically connects the monitor module 510 to themonitor 360 via the monitor's sensor port 362.

FIG. 5B illustrates a cable-connect module 540 having a case 542 and anauxiliary cable 550. The case 542 functions as for the direct-connectmodule 510 (FIG. 5A), described above. Instead of directly plugging intothe monitor 360, the cable-connect module 540 utilizes the auxiliarycable 550, which mimics the monitor end of a patient cable, such as apulse oximetry patient cable 140 (FIG. 1), and electrically connects thecable-connect module 540 to the monitor sensor port 362.

FIG. 5C illustrates a plug-in module 570 having a plug-in case 572 andan auxiliary cable 580. The plug-in case 572 is mechanically compatiblewith the plug-in chassis of a multiparameter monitor 370 and may or maynot electrically connect to the chassis backplane. The auxiliary cable580 mimics a patient cable and electrically connects the plug-in module570 to the sensor port 372 of another plug-in device. A direct-connectmodule 510 (FIG. 5A) or a cable-connect module 540 (FIG. 5B) may also beused with a multiparameter monitor 370.

In a multiparameter embodiment, such as described with respect to FIGS.13-14, below, a monitor module 500 may connect to multiple plug-indevices of a multiparameter monitor 370. For example, a cable-connectmodule 540 (FIG. 5B) may have multiple auxiliary cables 550 (FIG. 5B)that connect to multiple plug-in devices installed within amultiparameter monitor chassis. Similarly, a plug-in module 570 may haveone or more auxiliary cables 580 with multiple connectors for attachingto the sensor ports 372 of multiple plug-in devices.

Communications Adapter Functions

FIGS. 6-7 illustrate functional embodiments of a communications adapter.FIG. 6 illustrates a sensor module 400 having a sensor interface 610, asignal processor 630, an encoder 640, a transmitter 650 and atransmitting antenna 670. A physiological sensor 310 provides an inputsensor signal 612 at the sensor connector 318. Depending on the sensor310, the sensor module 400 may provide one or more drive signals 618 tothe sensor 310. The sensor interface 610 inputs the sensor signal 612and outputs a conditioned signal 614. The conditioned signal 614 may becoupled to the transmitter 650 or further processed by a signalprocessor 630. If the sensor module configuration utilizes a signalprocessor 630, it derives a parameter signal 632 responsive to thesensor signal 612, which is then coupled to the transmitter 650.Regardless, the transmitter 650 inputs a baseband signal 642 that isresponsive to the sensor signal 612. The transmitter 650 modulates thebaseband signal 642 with a carrier to generate a transmit signal 654.The transmit signal 654 may be derived by various amplitude, frequencyor phase modulation schemes, as is well known in the art. The transmitsignal 654 is coupled to the transmit antenna 670, which provideswireless communications to a corresponding receive antenna 770 (FIG. 7),as described below.

As shown in FIG. 6, the sensor interface 610 conditions and digitizesthe sensor signal 612 to generate the conditioned signal 614. Sensorsignal conditioning may be performed in the analog domain or digitaldomain or both and may include amplification and filtering in the analogdomain and filtering, buffering and data rate modification in thedigital domain, to name a few. The resulting conditioned signal 614 isresponsive to the sensor signal 612 and may be used to calculate orderive a parameter signal 632.

Further shown in FIG. 6, the signal processor 630 performs signalprocessing on the conditioned signal 614 to generate the parametersignal 632. The signal processing may include buffering, digitalfiltering, smoothing, averaging, adaptive filtering and frequencytransforms to name a few. The resulting parameter signal 632 may be ameasurement calculated or derived from the conditioned signal, such asoxygen saturation, pulse rate, blood glucose, blood pressure and EKG toname a few. Also, the parameter signal 632 may be an intermediate resultfrom which the above-stated measurements may be calculated or derived.

As described above, the sensor interface 610 performs mixed analog anddigital pre-processing of an analog sensor signal and provides a digitaloutput signal to the signal processor 630. The signal processor 630 thenperforms digital post-processing of the front-end processor output. Inalternative embodiments, the input sensor signal 612 and the outputconditioned signal 614 may be either analog or digital, the front-endprocessing may be purely analog or purely digital, and the back-endprocessing may be purely analog or mixed analog or digital.

In addition, FIG. 6 shows an encoder 640, which translates a digitalword or serial bit stream, for example, into the baseband signal 642, asis well-known in the art. The baseband signal 642 comprises the symbolstream that drives the transmit signal 654 modulation, and may be asingle signal or multiple related signal components, such as in-phaseand quadrature signals. The encoder 640 may include data compression andredundancy, also well-known in the art.

FIG. 7 illustrates a monitor module 500 having a receive antenna 770, areceiver 710, a decoder 720, a waveform processor 730 and a monitorinterface 750. A receive signal 712 is coupled from the receive antenna770, which provides wireless communications to a corresponding transmitantenna 670 (FIG. 6), as described above. The receiver 710 inputs thereceive signal 712, which corresponds to the transmit signal 654 (FIG.6). The receiver 710 demodulates the receive signal to generate abaseband signal 714. The decoder 720 translates the symbols of thedemodulated baseband signal 714 into a decoded signal 724, such as adigital word stream or bit stream. The waveform processor 730 inputs thedecoded signal 724 and generates a constructed signal 732. The monitorinterface 750 is configured to communicate the constructed signal 732 toa sensor port 362 of a monitor 360. The monitor 360 may output a sensordrive signal 754, which the monitor interface 750 inputs to the waveformprocessor 730 as a monitor drive signal 734. The waveform processor 730may utilize the monitor drive signal 734 to generate the constructedsignal 732. The monitor interface 750 may also provide characterizationinformation 758 to the waveform processor 730, relating to the monitor360, the sensor 310 or both, that the waveform processor 730 utilizes togenerate the constructed signal 732.

The constructed signal 732 is adapted to the monitor 360 so thatmeasurements derived by the monitor 360 from the constructed signal 732are generally equivalent to measurements derivable from the sensorsignal 612 (FIG. 6). Note that the sensor 310 (FIG. 6) may or may not bedirectly compatible with the monitor 360. If the sensor 310 (FIG. 6) iscompatible with the monitor 360, the constructed signal 732 is generatedso that measurements derived by the monitor 360 from the constructedsignal 732 are generally equivalent (within clinical significance) withthose derivable directly from the sensor signal 612 (FIG. 6). If thesensor 310 (FIG. 6) is not compatible with the monitor 360, theconstructed signal 732 is generated so that measurements derived by themonitor 360 from the constructed signal 732 are generally equivalent tothose derivable directly from the sensor signal 612 (FIG. 6) using acompatible monitor.

Wireless Pulse Oximetry

FIGS. 8-11 illustrate pulse oximeter embodiments of a communicationsadapter. FIGS. 8-9 illustrate a sensor module and a monitor module,respectively, configured to communicate measured pulse oximeterparameters. FIG. 10-11 illustrate a sensor module and a monitor module,respectively, configured to communicate a plethysmograph signal.

Parameter Transmission

FIG. 8 illustrates a pulse oximetry sensor module 800 having a sensorinterface 810, signal processor 830, encoder 840, transmitter 850,transmitting antenna 870 and controller 890. The sensor interface 810,signal processor 830 and controller 890 function as described withrespect to FIG. 2, above. The sensor interface 810 communicates with astandard pulse oximetry sensor 310, providing an LED drive signal 818 tothe LED emitters 312 and receiving a sensor signal 812 from the detector314 in response. The sensor interface 810 provides front-end processingof the sensor signal 812, also described above, providing aplethysmograph signal 814 to the signal processor 830. The signalprocessor 830 then derives a parameter signal 832 that comprises a realtime measurement of oxygen saturation and pulse rate. The parametersignal 832 may include other parameters, such as measurements ofperfusion index and signal quality. In one embodiment, the signalprocessor is an MS-5 or MS-7 board available from Masimo Corporation,Irvine, Calif.

As shown in FIG. 8, the encoder 840, the transmitter 850 and thetransmitting antenna 870 function as described with respect to FIG. 6,above. For example, the parameter signal 832 may be a digital wordstream that is serialized into a bit stream and encoded into a basebandsignal 842. The baseband signal 842 may be, for example, two bit symbolsthat drive a quadrature phase shift keyed (QPSK) modulator in thetransmitter 850. Other encodings and modulations are also applicable, asdescribed above. The transmitter 850 inputs the baseband signal 842 andgenerates a transmit signal 854 that is a modulated carrier having afrequency suitable for short-range transmission, such as within ahospital room, doctor's office, emergency vehicle or critical care ward,to name a few. The transmit signal 854 is coupled to the transmitantenna 870, which provides wireless communications to a correspondingreceive antenna 970 (FIG. 9), as described below.

FIG. 9 illustrates a monitor module 900 having a receive antenna 970, areceiver 910, a decoder 920, a waveform generator 930 and an interfacecable 950. The receive antenna 970, receiver 910 and decoder 920function as described with respect to FIG. 7, above. In particular, thereceive signal 912 is coupled from the receive antenna 970, whichprovides wireless communications to a corresponding transmit antenna 870(FIG. 8). The receiver 910 inputs the receive signal 912, whichcorresponds to the transmit signal 854 (FIG. 8). The receiver 810demodulates the receive signal 912 to generate a baseband signal 914.Not accounting for transmission errors, the baseband signal 914corresponds to the sensor module baseband signal 842 (FIG. 8), forexample a symbol stream of two bits each. The decoder 920 assembles thebaseband signal 914 into a parameter signal 924, which, for example, maybe a sequence of digital words corresponding to oxygen saturation andpulse rate. Again, not accounting for transmission errors, the monitormodule parameter signal 924 corresponds to the sensor module parametersignal 832 (FIG. 8), derived by the signal processor 830 (FIG. 8).

Also shown in FIG. 9, the waveform generator 930 is a particularembodiment of the waveform processor 730 (FIG. 7) described above. Thewaveform generator 930 generates a synthesized waveform 932 that thepulse oximeter monitor 360 can process to calculate SpO₂ and pulse ratevalues or exception messages. In the present embodiment, the waveformgenerator output does not reflect a physiological waveform. Inparticular, the synthesized waveform is not physiological data from thesensor module 800, but is a waveform synthesized from predeterminedstored waveform data to cause the monitor 360 to calculate oxygensaturation and pulse rate equivalent to or generally equivalent (withinclinical significance) to that calculated by the signal processor 830(FIG. 8). The actual intensity signal from the patient received by thedetector 314 (FIG. 8) is not provided to the monitor 360 in the presentembodiment. Indeed, the waveform provided to the monitor 360 willusually not resemble a plethysmographic waveform or other physiologicaldata from the patient to whom the sensor module 800 (FIG. 8) isattached.

The synthesized waveform 932 is modulated according to the drive signalinput 934. That is, the pulse oximeter monitor 360 expects to receive ared and IR modulated intensity signal originating from a detector, asdescribed with respect to FIGS. 1-2, above. The waveform generator 930generates the synthesized waveform 932 with a predetermined shape, suchas a triangular or sawtooth waveform stored in waveform generator memoryor derived by a waveform generator algorithm. The waveform is modulatedsynchronously with the drive input 934 with first and second amplitudesthat are processed in the monitor 360 as red and IR portions of a sensorsignal. The frequency and the first and second amplitudes are adjustedso that pulse rate and oxygen saturation measurements derived by thepulse oximeter monitor 360 are generally equivalent to the parametermeasurements derived by the signal processor 830 (FIG. 8), as describedabove. One embodiment of a waveform generator 930 is described in U.S.Patent Application Ser. No. 60/117,097 entitled “Universal/UpgradingPulse Oximeter,” assigned to Masimo Corporation, Irvine, Calif. andincorporated by reference herein. Although the waveform generator 930 isdescribed above as synthesizing a waveform that does not resemble aphysiological signal, one of ordinary skill will recognize that anotherembodiment of the waveform generator 930 could incorporate, for example,a plethysmograph simulator or other physiological signal simulator.

Further shown in FIG. 9, the interface cable 950 functions in a mannersimilar to the monitor interface 750 (FIG. 7) described above. Theinterface cable 950 is configured to communicate the synthesizedwaveform 932 to the monitor 360 sensor port and to communicate thesensor drive signal 934 to the waveform generator 930. The interfacecable 950 may include a ROM 960 that contains monitor and sensorcharacterization data. The ROM 960 is read by the waveform generator 930so that the synthesized waveform 932 is adapted to a particular monitor360. For example, the ROM 960 may contain calibration data of red/IRversus oxygen saturation, waveform amplitude and waveform shapeinformation. An interface cable is described in U.S. Patent ApplicationSer. No. 60/117,092, referenced above. Monitor-specific SatShare™ brandinterface cables are available from Masimo Corporation, Irvine, Calif.In an alternative embodiment, such as a direct connect monitor module asillustrated in FIG. 5A, an interface cable 950 is not used and the ROM960 may be incorporated within the monitor module 900 itself.

Plethysmograph Transmission

FIG. 10 illustrates another pulse oximetry sensor module 1000 having asensor interface 1010, encoder 1040, transmitter 1050, transmittingantenna 1070 and controller 1090, which have the corresponding functionsas those described with respect to FIG. 8, above. The encoder 1040,however, inputs a plethysmograph signal 1014 rather than oxygensaturation and pulse rate measurements 832 (FIG. 8). Thus, the sensormodule 1000 according to this embodiment encodes and transmits aplethysmograph signal 1014 to a corresponding monitor module 1100 (FIG.11) in contrast to derived physiological parameters, such as oxygensaturation and pulse rate. The plethysmograph signal 1014 is illustratedin FIG. 10 as being a direct output from the sensor interface 1010. Inanother embodiment, the sensor module 1000 incorporates a decimationprocessor, not shown, after the sensor interface 1010 so as to provide aplethysmograph signal 1014 having a reduced sample rate.

FIG. 11 illustrates another pulse oximetry monitor module 1100 having areceive antenna 1170, a receiver 1110, a decoder 1120 and an interfacecable 1150, which have the corresponding functions as those describedwith respect to FIG. 9, above. This monitor module embodiment 1100,however, has a waveform modulator 1200 rather than a waveform generator930 (FIG. 9), as described above. The waveform modulator 1200 inputs aplethysmograph signal from the decoder 1120 rather than oxygensaturation and pulse rate measurements, as described with respect toFIG. 9, above. Further, the waveform modulator 1200 provides anmodulated waveform 1132 to the pulse oximeter monitor 360 rather than asynthesized waveform, as described with respect to FIG. 9. The modulatedwaveform 1132 is a plethysmographic waveform modulated according to themonitor drive signal input 1134. That is, the waveform modulator 1200does not synthesize a waveform, but rather modifies the receivedplethysmograph signal 1124 to cause the monitor 360 to calculate oxygensaturation and pulse rate generally equivalent (within clinicalsignificance) to that derivable by a compatible, calibrated pulseoximeter directly from the sensor signal 1012 (FIG. 10). The waveformmodulator 1200 is described in further detail with respect to FIG. 12,below.

FIG. 12 shows a waveform modulator 1200 having a demodulator 1210, a reddigital-to-analog converter (DAC) 1220, an IR DAC 1230, a red amplifier1240, an IR amplifier 1250, a modulator 1260, a modulator control 1270,a look-up table (LUT) 1280 and a ratio calculator 1290. The waveformmodulator 1200 demodulates red and IR plethysmographs (“pleths”) fromthe decoder output 1124 into a separate red pleth 1222 and IR pleth1232. The waveform modulator 1200 also adjusts the amplitudes of thepleths 1222, 1232 according to stored calibration curves for the sensor310 (FIG. 10) and the monitor 360 (FIG. 11). Further, the waveformmodulator 1200 re-modulates the adjusted red pleth 1242 and adjusted IRpleth 1252, generating a modulated waveform 1132 to the monitor 360(FIG. 11).

As shown in FIG. 12, the demodulator 1210 performs the demodulationfunction described above, generating digital red and IR pleth signals1212, 1214. The DACs 1220, 1230 convert the digital pleth signals 1212,1214 to corresponding analog pleth signals 1222, 1232. The amplifiers1240, 1250 have variable gain control inputs 1262, 1264 and perform theamplitude adjustment function described above, generating adjusted redand IR pleth signals 1242, 1252. The modulator 1260 performs there-modulation function described above, combining the adjusted red andIR pleth signals 1242, 1252 according to a control signal 1272. Themodulator control 1270 generates the control signal 1272 synchronouslywith the LED drive signal(s) 1134 from the monitor 360.

Also shown in FIG. 12, the ratio calculator 1290 derives a red/IR ratiofrom the demodulator outputs 1212, 1214. The LUT 1280 stores empiricalcalibration data for the sensor 310 (FIG. 10). The LUT 1280 alsodownloads monitor-specific calibration data from the ROM 1160 (FIG. 11)via the ROM output 1158. From this calibration data, the LUT 1280determines a desired red/IR ratio for the modulated waveform 1132 andgenerates red and IR gain outputs 1262, 1264 to the correspondingamplifiers 1240, 1250, accordingly. A desired red/IR ratio is one thatallows the monitor 360 (FIG. 11) to derive oxygen saturationmeasurements from the modulated waveform 1132 that are generallyequivalent to that derivable directly from the sensor signal 1012 (FIG.10).

One of ordinary skill in the art will recognize that some of the signalprocessing functions described with respect to FIGS. 8-11 may beperformed either within a sensor module or within a monitor module.Signal processing functions performed within a sensor module mayadvantageously reduce the transmission bandwidth to a monitor module ata cost of increased sensor module size and power consumption. Likewise,signal processing functions performed within a monitor module may reducesensor module size and power consumption at a cost of increasetransmission bandwidth.

For example, a monitor module embodiment 900 (FIG. 9) described abovereceives measured pulse oximeter parameters, such as oxygen saturationand pulse rate, and generates a corresponding synthesized waveform. Inthat embodiment, the oxygen saturation and pulse rate computations areperformed within a sensor module 800 (FIG. 8). Another monitor moduleembodiment 1100 (FIG. 11), also described above, receives aplethysmograph waveform and generates a remodulated waveform. In thatembodiment, minimal signal processing is performed within a sensormodule 1000 (FIG. 10). In yet another embodiment, not shown, a sensormodule transmits a plethysmograph waveform or a decimated plethysmographwaveform having a reduced sample rate. A corresponding monitor modulehas a signal processor, such as described with respect to FIG. 8, inaddition to a waveform generator, as described with respect to FIG. 9.The signal processor computes pulse oximeter parameters and the waveformgenerator generates a corresponding synthesized waveform, as describedabove. In this embodiment, minimal signal processing is performed withinthe sensor module, and the monitor module functions are performed on thepulse oximeter parameters computed within the monitor module.

Wireless Multiple Parameter Measurements

FIGS. 13-14 illustrate a multiple parameter communications adapter. FIG.13 illustrates a multiple parameter sensor module 1300 having sensorinterfaces 1310, one or more signal processors 1330, a multiplexer andencoder 1340, a transmitter 1350, a transmitting antenna 1370 and acontroller 1390. One or more physiological sensors 1301 provide inputsensor signals 1312 to the sensor module 1300. Depending on theparticular sensors 1301, the sensor module 1300 may provide one or moredrive signals 1312 to the sensors 1301 as determined by the controller1390. The sensor interfaces 1310 input the sensor signals 1312 andoutput one or more conditioned signals 1314. The conditioned signals1314 may be coupled to the transmitter 1350 or further processed by thesignal processors 1330. If the sensor module configuration utilizessignal processors 1330, it derives multiple parameter signals 1332responsive to the sensor signals 1312, which are then coupled to thetransmitter 1350. Regardless, the transmitter 1350 inputs a basebandsignal 1342 that is responsive to the sensor signals 1312. Thetransmitter 1350 modulates the baseband signal 1342 with a carrier togenerate a transmit signal 1354, which is coupled to the transmitantenna 1370 and communicated to a corresponding receive antenna 1470(FIG. 14), as described with respect to FIG. 6, above. Alternatively,there may be multiple baseband signals 1342, and the transmitter 1350may transmit on multiple frequency channels, where each channel coveysdata responsive to one or more of the sensor signals 1314.

As shown in FIG. 13, the sensor interface 1310 conditions and digitizesthe sensor signals 1312 as described for a single sensor with respect toFIG. 6, above. The resulting conditioned signals 1314 are responsive tothe sensor signals 1312. The signal processors 1330 perform signalprocessing on the conditioned signals 1314 to derive parameter signals1332, as described for a single conditioned signal with respect to FIG.6, above. The parameter signals 1332 may be physiological measurementssuch as oxygen saturation, pulse rate, blood glucose, blood pressure,EKG, respiration rate and body temperature to name a few, or may beintermediate results from which the above-stated measurements may becalculated or derived. The multiplexer and encoder 1340

-   -   combines multiple digital word or serial bit streams into a        single digital word or bit stream. The multiplexer and encoder        also encodes the digital word or bit stream to generate the        baseband signal 1342, as described with respect to FIG. 6,        above.

FIG. 14 illustrates a multiple parameter monitor module 1400 having areceive antenna 1470, a receiver 1410, a demultiplexer and decoder 1420,one or more waveform processors 1430 and a monitor interface 1450. Thereceiver 1410 inputs and demodulates the receive signal 1412corresponding to the transmit signal 1354 (FIG. 13) to generate abaseband signal 1414 as described with respect to FIG. 7, above. Thedemultiplexer and decoder 1420 separates the symbol streamscorresponding to the multiple conditioned signals 1314 (FIG. 13) and/orparameter signals 1332 (FIG. 13) and translates these symbol streamsinto multiple decoded signals 1422, as described for a single symbolstream with respect to FIG. 7, above. Alternatively, multiple frequencychannels are received to generate multiple baseband signals, each ofwhich are decoded to yield multiple decoded signals 1422. The waveformprocessors 1430 input the decoded signals 1422 and generate multipleconstructed signals 1432, as described for a single decoded signal withrespect to FIGS. 7-12, above. The monitor interface 1450 is configuredto communicate the constructed signals 1432 to the sensor ports of amultiple parameter monitor 1401 or multiple single parameter monitors,in a manner similar to that for a single constructed signal, asdescribed with respect to FIGS. 7-12, above. In particular, theconstructed signals 1432 are adapted to the monitor 1401 so thatmeasurements derived by the monitor 1401 from the constructed signals1432 are generally equivalent to measurements derivable directly fromthe sensor signals 1312 (FIG. 13).

A physiological measurement communications adapter is described abovewith respect to wireless communications and, in particular, radiofrequency communications. A sensor module and monitor module, however,may also communicate via wired communications, such as telephone,Internet or fiberoptic cable to name a few. Further, wirelesscommunications can also utilize light frequencies, such as IR or laserto name a few.

A physiological measurement communications adapter has been disclosed indetail in connection with various embodiments. These embodiments aredisclosed by way of examples only. One of ordinary skill in the art willappreciate many variations and modifications of a physiologicalmeasurement communications adapter within the scope of the claims thatfollow.

1. A communications adapter comprising: a sensor interface configured toreceive a sensor signal; a transmitter that modulates a first basebandsignal responsive to said sensor signal so as to generate a transmitsignal; a receiver that demodulates a receive signal corresponding tosaid transmit signal so as to generate a second baseband signalcorresponding to said first baseband signal; and a monitor interfaceconfigured to communicate a waveform responsive to said second basebandsignal to a sensor port of a monitor, said waveform adapted to saidmonitor so that measurements derived by said monitor from said waveformare generally equivalent to measurements derivable from said sensorsignal.
 2. The communications adapter according to claim 1 furthercomprising a signal processor having an input in communications withsaid sensor interface, said signal processor operable to derive aparameter responsive to said sensor signal, said first baseband signalresponsive to said parameter.
 3. The communications adapter according toclaim 2 wherein said parameter corresponds to at least one of a measuredoxygen saturation and a pulse rate.
 4. The communications adapteraccording to claim 3 further comprising a waveform generator thatsynthesizes said waveform from a predetermined shape.
 5. Thecommunications adapter according to claim 4 wherein said waveformgenerator synthesizes said waveform at a frequency adjusted to begenerally equivalent to said pulse rate.
 6. The communications adapteraccording to claim 4 wherein said waveform has a first amplitude and asecond amplitude, said waveform generator configured to adjusted saidamplitudes so that measurements derived by said monitor are generallyequivalent to said measured oxygen saturation.
 7. The communicationsadapter according to claim 1 wherein said sensor interface is operableon said sensor signal to provide a plethysmograph signal output, saidfirst baseband signal responsive to said plethysmograph signal.
 8. Thecommunications adapter according to claim 7 further comprising awaveform modulator that modifies a decoded signal responsive to saidsecond baseband signal to provide said waveform.
 9. The communicationsadapter according to claim 8 wherein said waveform modulator comprises:a demodulator that separates a first signal and a second signal fromsaid decoded signal; an amplifier that adjusts amplitudes of said firstand second signals to generate a first adjusted signal and a secondadjusted signal; and a modulator that combines said first and secondadjusted signals into said waveform.
 10. The communications adapteraccording to claim 9 wherein amplitudes of said first and second signalsare responsive to predetermined calibration data for said sensor andsaid monitor.
 11. A communications adapter method comprising the stepsof: inputting a sensor signal at a patient location; communicatingpatient data derived from said sensor signal between said patientlocation and a monitor location; constructing a waveform at said monitorlocation responsive to said sensor signal; and providing said waveformto a monitor via a sensor port, said waveform constructed so that saidmonitor calculates a parameter generally equivalent to a measurementderivable from said sensor signal.
 12. The communications adapter methodaccording to claim 11 wherein said communicating step comprises thesubsteps of: deriving a conditioned signal from said sensor signal;calculating a parameter signal from said conditioned signal; andtransmitting said parameter signal from said patient location to saidmonitor location.
 13. The communications adapter method according toclaim 12 wherein said constructing step comprises the substep ofsynthesizing said waveform from said parameter signal.
 14. Thecommunications adapter method according to claim 11 wherein saidcommunicating step comprises the substeps of: deriving a conditionedsignal from said sensor signal; transmitting said conditioned signalfrom said patient location to said monitor location.
 15. Thecommunications adapter method according to claim 14 wherein saidconstructing step comprises the substeps of: demodulating saidconditioned signal; and re-modulating said conditioned signal togenerate said waveform.
 16. The communications adapter method accordingto claim 11 wherein said providing step comprises the substeps of:inputting a monitor signal from an LED drive output of said sensor port;modulating said waveform in response to said monitor signal; andoutputting said waveform on a detector input of said sensor port.
 17. Acommunications adapter comprising: a sensor interface means forinputting a sensor signal and outputting a conditioned signal; atransmitter means for sending data responsive to said sensor signal; areceiver means for receiving said data; a waveform processor means forconstructing a waveform from said data so that measurements derived by amonitor from said waveform are generally equivalent to measurementsderivable from said sensor signal; and a monitor interface means forcommunicating said waveform to a sensor port of said monitor.
 18. Thecommunications adapter according to claim 17 further comprising a signalprocessor means for deriving a parameter signal from said conditionedsignal, said data comprising said parameter signal.
 19. Thecommunications adapter according to claim 18 wherein said waveformprocessor means comprises a means for synthesizing said waveform fromsaid parameter signal.
 20. The communications adapter according to claim17 wherein said data comprises said conditioned signal and said waveformprocessor means comprises a means for modulating said conditioned signalin response to said monitor.